The present invention relates to low insertion loss connection of an antenna to a mobile radio, and more particularly to low insertion loss connection of an antenna to a satellite telephone. Even more particularly, the present invention relates to low insertion loss connection of an antenna to a satellite telephone with a swivel collar that allows a retractable antenna to swivel when deployed. Even more particularly, the present invention relates to a satellite telephone with a swivel collar that has two or more fixed detente positions to allow the user to fix an angle of swivel to one of the detente positions depending on whether the user holds the telephone in a left or right hand so that the antenna is pointing approximately vertically upwards in either case. Even more particularly, the present invention relates to a satellite telephone with a swivel collar and antenna slidable within the swivel collar so that the antenna can retract into a body of the telephone for protection from the elements, and against knocks and bumps as well as to keep maintain the appearance of the telephone as neat and tidy. Even more particularly, the present invention relates to a satellite telephone with a swivel collar and antenna slidable within the swivel collar so that the antenna is in an upright position, pointing vertically upwards and more or less in a direction of a satellite, ready to receive a call even when the antenna is in a retracted position as long as the telephone is stowed upright in a shirt pocket or jacket, on a belt clip, or left standing upright on a flat surface like a desk top or table. Even more particularly, the present invention relates to a satellite telephone with a swivel collar that has an antenna matching circuit built into it to allow a relatively lesser number of connections passing through a swivel joint for better reliability than in a case where the matching circuit is separate from the antenna, and to allow the antenna to be made shorter than in another case where the matching circuit is built into the antenna.
In non-satellite transceivers, such as conventional cellular telephones, a connection to an external vehicular antenna can be made through a radio frequency connector normally located on the bottom of the telephone. In order to prevent both the phone antenna and the external vehicular antenna from radiating and/or receiving radio frequency energy at the same time, which can cause phasing and other problems, a radio frequency switch in the conventional cellular telephone switches internal connections from the telephone antenna to the external vehicular antenna connected to the radio frequency connector, when a connection is detected.
In satellite transceiver applications, such as in satellite telephones, the use of a radio frequency switch for the purpose of switching internal connections from the phone antenna to the external vehicular antenna is not desirable due to the high insertion loss of the radio frequency switch. This high insertion loss is particularly problematic in satellite telephones because of the limited loss budget due to the greater distance between the satellite telephone and an earth orbit satellite with which it communicates. In order to make up this loss on the satellite side, by building a more sophisticated satellite, extremely high costs would be involved, such as on the order of 40 million dollars.
One way in which to eliminate the radio frequency switch is to simply use a detachable connector to connect the phone's antenna to the satellite telephone, and when use of the external vehicular antenna is desired to remove the telephone antenna and to connect vehicular antenna to the site on the satellite telephone from which the telephone antenna was removed. This approach is, however, awkward and time consuming, and therefore not highly desirable.
Another approach is to employ an inductive coupler that, when the satellite telephone is inserted into a docking adaptor in the vehicle, surrounds the telephone antenna (or a portion thereof) providing an inductive link between the external antenna and the satellite telephone. This approach, however, fails to achieve direct contact or close capacitive coupling between the vehicular external antenna and the satellite telephone, and thus also suffers from high insertion loss.
Another difficulty faced in a satellite telephone environment is the need to angle adjust or swivel the telephone antenna. This ability to angle adjust the antenna so as to aim the antenna toward the satellite with which it is communicating is needed because the telephone antenna's gain pattern is directional, and in a hand-held satellite telephone, a user is limited as to the angle at which the satellite telephone can be held in order to aim the antenna while at the same time maintaining the satellite telephone itself in a useable position near the user's ear and mouth.
As a result, all presently-available satellite telephones, and most global positioning system receivers for that matter, include a swivel joint at the attachment of antenna to the telephone or receiver. When the antenna is completely folded against the satellite telephone or global positioning system receiver's housing, it is in a storage position, and by swiveling the antenna up so as to aim it at the satellite or satellites with which it is communicating, the antenna is placed into a deployed position.
This approach however fails to address the problem that the antenna is alongside the housing of the telephone in the stowed position and not adequately protected from the elements and against knocks and bumps, as well as not in line with the appearance of a whole and integral unit. This approach also fails to address the problem that the antenna is not able to receive a call when it is in the stowed position because it is pointing in a wrong direction.
Another approach is to have a telescoping antenna, similar to antennas commonly used with portable AM/FM broadcast radio receivers, where a lower antenna element pivots relative to a housing body. This approach, however, fails to allow the antenna to slide into the housing of the radio for full retraction and protection.
Yet another approach is to have a pivot on the antenna element itself with the antenna and pivot together slidable into a channel of the radio receiver's housing body. This approach, however, adds to the length of the antenna because a matching circuit has to be placed within the antenna element above the pivot, as a connection between the matching circuit and the antenna has to be rigid for impedance matching, and therefore cannot be routed through the swivel joint.
The present invention advantageously addresses the above and other needs.